Conventional horizontal skylights suffer from poor sunlight collection when the sun is low in the sky, i.e., when the sun's elevation angle is small. This poor low-sun-angle performance leads to poor lighting in the wintertime in most moderate latitudes, and to poor lighting early and late in the day in all locations. Previous attempts to solve this problem have sometimes used expensive tracking reflectors above the skylight penetration into the building, or sometimes used fixed reflectors or prismatic lenses above the skylight penetration with less than adequate performance.
Embodiments of the skylight described herein use multiple stationary tilted reflectors aimed in different compass directions, including inverted pyramidal or wedge geometry to enhance the light output of a skylight using a conventional horizontal penetration into the building. The reflectors are made of very low cost metallized polymer film, and configured to maximize the useful lumen output of the skylight over the whole day and over the whole year. Thus, the light distribution under the horizontal penetration is improved by directing more light vertically into the working space beneath the roof penetration rather than horizontally onto walls and into the building occupants' eyes, creating glare and discomfort.
FIG. 1 illustrates the summer and winter sun and the angle of incident upon the transparent dome 4 (FIG. 3). The angle of incident of the summer sun with respect to level ground or the horizon is shown as θs. θs is shown generally, but may represent of a metric of the summer sun, such as an average daytime angle, an average peak angle, peak angle etc. Similarly, θw is the angle of incident of the winter sun with respect to the horizon. θw may also be representative of some metric of the winter sun. As noted above, in some cases it may be advantageous to capture the winter sun while shading the summer sun.
FIG. 2 is an illustration of the angle of incident during the day. As shown, θe is the angle of the sun in the evening, for example 4 pm, whereas θm is the angle of the sun in the morning at for example 10 am. The values used for θe and θm may as described above be chosen as averages, peaks, or corresponding to or biased to specific times. θe and θm need not be the same. FIG. 2 also shows the angle of the midday sun θmd. In warmer climates the midday sun may unnecessarily heat the interior of the building or provide excessive glare and thus it may be advantageous to limit the light during these periods.
Embodiments of the skylight described herein include multiple stationary tilted reflectors aimed in different compass directions, including inverted pyramidal or wedge geometry, to increase the daily and annual light output of a skylight using a conventional horizontal roof penetration. The multiple stationary reflectors are oriented and tilted to provide not only higher light output over more hours of the day and year, but also more downwardly aimed light into the working space beneath the roof penetration. Thus, both the quantity and quality of the natural lighting inside the building are improved. The greater quantity of daylight saves more energy for conventional electrical lighting, improving the economics of the skylight, and the better quality of the light improves working conditions for the occupants of the building. In addition, reducing summer time or midday sun also has the advantages of reducing cooling cost and excessive glare.
The disclosed subject matter presents a novel skylight for providing natural lighting to the interior of a building. The skylight includes a transparent dome rising above a roof of the building and having a light passage at one end to allow light into the interior of the building from the exterior of the building. A first stationary and tilted reflective surface faces a first compass direction and additional stationary and tilted reflective surfaces each face a respective compass direct, where the first compass direction and the respective compass directions are not the same, but each have of the first and additional surfaces have a common vertical component. The reflective surfaces of the skylight are within the transparent dome.
The disclosed subject matter also presents a novel device for passively providing light from a source external to a building to an interior of a building. The device includes a transparent dome projecting into the exterior of the building with a light passage from the interior to the exterior of the building. In the transparent dome, a plurality of fixed reflective surfaces are positioned, each reflective surface defined by a vector normal to their reflective surface having an azimuth direction, and an angle with respect to the horizon. The vectors associated with the fixed reflective surfaces are different from each other vector.
The disclosed subject matter also includes a novel method for providing natural lighting to the interior of a building. The method includes providing a skylight with a plurality of reflectors aimed in different compass directions and a light passage to the interior of the building. The plurality of reflectors are tilted to direct light below a threshold angle of incident with the horizon into the light passage and to prevent light above a second threshold angle of incident from entering the light passage; and fixed in place prior to the installation of the skylight. The skylight is installed above the light passage and light below the threshold is directed into the light passage and light above the second threshold is prevented from entering the light passage by the plurality of reflectors.
These and many other advantages of the present subject matter will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.